Thermoplastic adhesive compositions



Patented Oct. 7, 195 2 'rnamuorms'rlo ADHESIVE COMPOSITIONS i T ciiaiph o.- :raceam trlamnem, .N. an Alfred.

G, Batiaglia, New York, N. Y., assignors' to National Starch Br'oducts Inc., vNewYork, N. Y., a corporation of. Delaware No Drawing. Application July 21, 1.949.. Serial No. 106,092

8 (Ill-aims. (Cl. IDS-+170 This invention relatesto an improved thermoplastic adhesive and a method 10: manufacture thereof. More specifically, it relates to an. adhesive which produces .a'nlm which is dryand non-tacky under room-temperature conditions.

but which becomes tacky and'ihigh'lyndhesiveupon the subsequent application of heat.

An object of our inventioni's to produce a thermoplastic adhesive which may be applied to labels, cartons, boxes, and other surfaces, and which will dry to a 'filmso 'non-tackythat during the manufacture, shipping, storage, and useof these products, they 'willn'ot tend to block-that is, to stick to one anotherijeitherpermanently or momentarily, but which-lat the time/of application, when heat is applied, 'wiliqattain their full adhesive power. Y

Thermoplastic-adhesivecompositionsordinarily consist of a thermoplastic polymeric material such as a resin base together with a plasticlzing material. The 'plasticizer is necessary in order that the composition maybecome sumcient-ly adhesive and tacky at the desired temperature and (where desired) to attaintdelayedtack. Delayed tack" refers to the characteristic "whereby" a thermoplastic composition, after being heated-to a temperature where it becomes adhesive and tacky, thereafter-retains its tacky'adhesive quality 'for an interval after heating is discontinued.

This property is or interest for certain industrial applicationathough notall. Howcvernthe used a plasticizer is -essential *in {practically all com-, mercial thermoplastic .adheslve compositions.

The use of ordinaryliquidplasticizers-such as.

for example, trioresyl phosphate and dibutyl 'phthalate-wasmarked by'the disadvantage that these liquid plasticizers activated the resln base immediately upon contact therewith, even before heating took "place; In other words, aeomposition containing a resin" base together with an effective quantity of a liquid p'lasticizer, when spread upon labels, carton iiaps,"or'similar surfaces, frequently resulted in a film which was tacky even at rooznjtemperature. A's already exp1ained,-this tackinessrepresented agrave dis- 1 advantage in the-manuiactura storage, and use of such adhesive-coated productsw We have now discovered thataan excellent thermoplastic adhesive composition, whose ==dried films are-"non-tackyrsmooth, undiree hom grahi- Whether coalesced by heating orsolution, the result is a clear, homogeneous fluid wherein the thermoplastic polymer and plasticizer no longer exist in physically independent relationship, but are mutually dissolved-or dispersed in one another. Regardless of'w-hether thiscoalescing of the polymer and plasticizer results from the heat or solution in a commonsolvent, or whether there be involved a liquid or solid solution, the neteffeet is a coalescing of the thermoplastic polymer and "plasticizer; Thus, when using the term coalescing" in the claims, we comprehend both the heat-iusion or the common solvent methods ot combining the-thermoplastic polymer andplasticizer. 7

:Step .IL--.Emulsifying the rplasticizedrthermoplastic :polymer :ofstep .I in watercontaming an appropriate emulsifying agent.

yf-ying agent. ,nsrthe emulsion cools, there occurs within each globule a separation of a portion-10f the normally solidplasticizer. Thus, eachiglobule lathe-cooled emulsion may be pictured as aneutity consisting of a core of partially plasticized thermoplastic polymer :(sincei-t is clear that not :all of the vpiasticizer separates tout) surrounded and coated by the separated solid :plastieizer, the

entire unit being'further protectedby a film of the emulsifyinglagent. When this emulsion, or dispersion; is coated upon :a surface and permitted to dry, there results a smooth, non+tack-y film, Although the ,prior coa'lescing of "the thermoplastic polymer and' plasticizerwould have been presumed :toresult in a :tacky, adhesive mass, it is belleved that the fact that each zpartic'le :oi

the thermoplastic polymer and solid plasticizer; ,1";

and by smaller particles of plasticizer; the film, therefore, being smooth and non-grainy, asg well as non-tacky, at ordinary room temperatures.

As the adhesive base inour'p oduct, we may use any polymeric material, orhcomblna'tion "or;

such materials, which are characterized by ther f moplastic properties. The particular thermo;

plastic base may be chosen to meet specificicongfditions and circumstances under which the ad= hesive is to be employed. Examples of such 8 25 and plasticizer, it is only necessary to melt tothermoplastic bases include polyvinyl acetate, .polyvinyl. chloride, polyvinyl acetatet-chloride .copolymenwpolyvinylidene chloride (Saran), methacrylic resin (Acrysols), non-drying -alkyds.,nondrying phenolics, polystyrenes,polyamides, thermoplastic cellulose esters and others, coumarone- .indeneyresins, ester: gums,; synthetic rubber, types, and .theslikem For. brevity, we'shall sometimes reierghereina'fter. to-such thermoplastic materials :as resins. or jthermoplastic resins," since such resins-constitute; a: large class .of such materials.

"As the plasticizer, we may use .any -one,- or 'moreithan: one, which .is solid atinormal room temperatures. Examplesof. such plasticizers are diphenyl' iphthalate triphenyl phosphate, .di-

'phenyl; tridichlorphenyl phosphate, Santowax M and 'P;;(a-nd which :we .believe to be meta,-: and para-:terphenyls); triparatertiary v.butylpphenyl wphosphatelsold under the trade name-Plasticizer x7)',. n.-;cyclohexyl. *paratoluene: sulphonamide (suclipfo'r. .example,= as. is sold :under: the trade "name Santicizer 1-H) ,'ethyl' ortho benzoyl=.benzo- -ate.'(as sold. under the vtradelname Ketonone E) a suitable mixture of orthoand para-toluene sulfon'amides (such, for examp1e,:as issold under 7 "thez t'ra'de name' Santicizer 9), and .dicyclohexyl phthalate. I Here, too, :th'e plasti'cizer may; be chosenin the light oi'the'particular' thermoplastic polymeric material employed; following-data on compatibilities of plasticizers-and resins-now *widelyknoWh.

With reference to the proportiori'bf plasticizer to be used, it is obviousthat- 'this may vary over 21 very wide range, not only because of the great "number of possible resins and plasticizers availablefi and' the variancein their compatibilities, 6

but-because of ithe variation in degree f *plasticization andtack requireddrrthe final product,

-for varying commercial applications; "The qua'ntlty; of plasticizer to be used generally varies with the "molecular weight of thetparticular resin base ln the composition-as:wellfas witlr the degree of eventual plasticity and "tack de'sire'd in the fina adhesive. "Thus, :a lowmo'leclrl'ar weight-polyvinyl acetate -.willrequire less.pl'asticization' than high molecular weight polyvinyl iacetate or. high molecular, weight polyvinylidene chloride or meth- -acry1ates. As for the minimum quantity .ofplasticizer to be used, thisobviouslywillalsovary with the particular plasticizer --and ,:resin:-p1asticizercombination; .but,.in all cases; the-amount 4o hegexamplslsiv.en

of plasticizer should be in excess of that which remains compatible and merged with a given resin after the steps of melting or dissolving the resin and plasticizer, emulsifying, and cooling 5 have taken place. It is'well known to those in the art that any given plasticizer has a known or measurable degree of compatibility with a given resin, this degree of compatibility varying as between different resins and plasticizers. For

any particular resin,'there is a ratio oga given plasticizer which will remain in a state coalescence with the sin (re compatible), whereas anri quan'tityaliove that lmiitiwill not remain in .;.aj;state of coalescence with the resin for any substantial length of time (i. e., incompatible). ;'But,i's'ince it is a fundamental requirement of our invention that there be a separation of solid A pla's cizerj'from'the' fused or dissolved resin-plasticiier inas'sl' 't*fo llows that enough plasticizer to compensate for that quantity within the resin, and to have 3 'pr esentanexces's of plasticizer which will separate out. To determine the amount of plasticizer to be-used for any given combination of resin .gether a small portiom spread the fluid on a glass .or similar surface w to cool', and note whether separation occurs. Suc h separation is ordinarily 'obyiou s to the paired; eye, although microscopic examination may also'f be employed. If no sepause in making our pro uct. Further increases in plas i i er s advf a' wi dep upon other.fa ctors,' including the temperature or range of temperiatures at which" it. is .desired that the dried adhesive fil' shallbec'ome tacky, etc. In I 'below, .f.theplasticizer is in the proportion.byweight'bf o'nepartof the resin to one to five parts of the plastic'izerl' In f The procedure inmalgingour product is simple, merely comprising. jusin'g as, for example, by, heating-thi thermoplastic polymer such as .{the'resinandIplasticizerto 'meltthem to a homoseneeuszfi ld ter e'g eu nelthe ho fluid. with agitation, i hot lwater. (preferably sub- F') -containing"one or more will be obvious to those hat the, amount of water e particular solids content LL12. ,the final, product. Any ents, or protective colloids H v h, for example, as poly- .vinyl alco l.-adlee ylzsqdiumisul os c o the-type sold y Ameri an C an m .&: Chemical r or t on .un c 'zthe -:..t f le:- a;ne A r 0T), 5 .3 q us.s l -tionip. an-a k l a yl po s/ galcohol (of thmtype sold bygBohm &'Haas under "the trade name Triton.NE),,;longrchain fatty ac d t a stersofhfix fio nhydr n po oxyallcylene deliv'i tives of. these partial esters (sold by the Atlas. lfiowder Company :under the dipl ma-:

ltra v m pans: n .Tw ens-rres ctiv ly) dium carboxymethylcellulose,;alginates, and ben- JtQnite; The said fSpan are,.essentially partial esters of the common fatty acids (lauric, 'palmitic, stearic; ,-and o leic); and hexito1 anhyidrides -(hexitans, and-hexideskidfirived from sor- -biItO finanflfiesmbltan monuna mitat z a of the plasticizer separates'from'the resin ing the resin particles and preventingftackrness. This separation of V the iplasticizer Iromfthe resin 60---sor,bitan monostearate-l The said "Tw e are derivedirom the. Span products byladdin polyoxyethylenochains to the non-esterifled ,hy-

droxyls; Tween. e0,-DQ 0Xyethylene sorbitan monopalmitate; Tween 60-:polyoxyethylenesorbitan monostearate, p,

A itation of the plasticiaed resin intfwater -is continued until a homogeneous emulsion, is

formed, the temperature being maintained above the softening point or the plasticized resin. Then the emulsion ispermitted to cool, and is ready for,use as an adhesive: I v I o M As has already beenindicated, the- 'step of heati ing and fusing the thermoplastic polymer such as-the resin and plasticizer maybe replacedby.

dissolvingthetwozcom qnents ina "common sol vent and, therefore, continuing with the emu sification procedure as above indicated, although by the latter "method, the water contamin'g "the emulsifyinga'gentneedfnotbeheated. j

We have'hereindesribed the two major steps necessary" for the preparation of "our product+ namely, coalescing of resin-plasticizer '(by melting or solution) and emulsiflcation. However, we

have discovered that, additional improved properties maybe obtained byemploying one ormore of the iollowing' additionalsteps: I o v I (a) In order to giveftheultimate 'drl'edadhesive film (prior to heat activation) an even smoother,

moreslippery surfacef wlth iurther'increased resistance to blocklng, we sometimes incorporate with the resin andplasticizera minor proportion of a waxor waxy substancasuo ior example, as opal wai;candjeli1,1a wax, andthe like.

is desirable and, indeed, essential to suepm ess On the otherhand; when the dried; adhe si've surface; is, finally heated, in ordeni toffuse about full tackihess and adhesive strengthfl i't is then important that thefplasticizer shalllremain merged andfcompatiblejwith the resin. fTothiS end, We prefer to add, a'material knownin art as a fluX -th'@tjfi5,, a substance 'whichlw'ill promotegtfhe. ultimate fusion of resin and plastie cizer and whichwfll'thereaiter increase the gloom patibilityj'of the resin and .plastlic'izer, As (th s; agents, it isfjgenjerally' preferred to use rosin; derivatives, such Ta's'f the various resinates, or the dispersions of modified resins sold under the trade name Dres'inols, 'Dresinol 40 being an rammoniacal. dispersion. prepared from a partially isomeriz'ed light colored rosin; the dispersion having a total solids content of approximately-910%. We ordinarily preierto' add the ilux to the cooled emulsion of the plastioizedresln (in; other words. aiter'the completion of step 11).. The quantity of flux may be varied over a widerange, depending chiefly upon: thev particular :flux chosen. and the compatibility :of the particular combination or resin-plasticizer; inguestiomhut we, ordinarily employ no} more,than; about 20% of-"the fluxffsole gee-)1its-a already peeal'pointd. out that when thermal plasticized resin emulsion is spread upon numerable globules or particles, each comprising a, comet partially plastlcizediresin surrounded ,by solid plasticizer plus an outer coating-of the emulsifying agent. This is, therefore, essentially a discontinuous film; When the film is deposited upon surfaces such, for example, as on paper labels-which maybe subject to flexin and, bending, there sometimes occurs a cracking or powdering oil of some oiijthe dry adhesive. In order to avoid, such a conditlon i-t is advisable to I add to the emulsion a minor proportion of a suhstance whlch will form a continuous film end-a t lbi d r for the ad es v l u Such abinder may consistoi suitable substancejfla able of formlng a continuous, relatively flexible film. Representative suitable binding agents are the emulsions or dispersions, either singly or in admixture, of natural or synthetic rubbers. or resins, such as a copolymer of acrylonitrileuand butadienedispersion (as sold under the trade name Hycarlewaqueous dispersions of acrylic polymers fias, for ,xexamplepAcrysols, (3-9, WA-5, ER 011MB), polyvinyl acetate, polyvinyl chloride. .Other suitableafilm-iorming binding agents will readily; suggest lthemselves. to those iamiliarwith theart. v werprefer to keep the proportion of binder at a and find than-quantities less than l0%.--(the solids contentot the binder being 'cale culatedupon the; totalweight of the adhesive emulsion) are ordinarily sumcient.

The following examples will further illustrate the embodiment of our invention:

l :fExample l n andjinithe suhsequent examples all pan iaii n r by? "i tr 'Ten lo'l pa'rts pdlyst ,rene (molecular weight 1 100 audio par-ts diphenyl 'phthalate heated together atgapproximately ng 'a'clear fluid. WhiIe'stfll at this H the"flui'd is poured into a solution of 6 part I ,a 2 5%' aqueous'solution of Aerosol OT and parts'polyvinyl alcohol (of the grade I sold under the trade name Elvanol -42) in'75.5

parts water; the solution being at a temperature of approximately 19031 Constantagita- 'tiori ls' maintained, resulting in ahomogeneous emulsion. {Ijhe emulsionis It'hen permittedv to v.

A portion of this emulsion was spread upon one surface 0160 lb. kra ftpa'per, by means of a doctor jbladeor' a standard roller ocating machine, Thathickness of thewet film was ;0015 inch. After drying at room temperature for 24 hours, the film was smooth,non-grainyg and en- 'tirely free'o'f tackiness. j'Upon heatirigto 1'70" F.,' the film beeame'j powerfullyftacky and adhesive; After heat was withdrawn the' film remainedtacky for aperiodof 79' seconds, before 'returningtofitsnonctackystate;

& lt'mmpwn Ten (10) par-ts'polyamide resin, 2. baseres'in formed by the reaction of the dimerized and 'trimerized linoleic and linolenic acids of soybean oil ids-content) :based upon the, total weight 'of' the plasticized resin-water emulsion.

with :ethylene diamine. (of the type sold by General Mills. under the. trade name Pol yamide No. 93) are melted together with so parts dicyclohexyl phthalate,, lf-ormingz'af clear fluid. While :stillhot-and fluid, this plasticize'dire'sin is poured,

with constant agitation, into 80 parts of water,

7 heated to 180 F., and containing dissolved therein" 4 parts sodiumj carboxymethylcellulose -(of the type{ sold- 1 under="- the trade name Sodium CMC4WM1 with '6 parts Triton NE. The resulting emulsion is permitted to cool. Surfaces coat-- ed with-this emulsionare found to possess the advar'itageous properties described in Example 'I.

. Ez m e lf Ten parts ethyl cellulose, low viscosity, are heated together with 40-parts triphenyl phosphate, until both are-melted. The hot,- clear fluid is poured, with constant agitation; into 70- parts of water heated to-195'F. and" containing dissolved therein 45 parts of polyvinyl alcohol (of thetype sold under the trade name Elvanol 52-22), 3 parts Span N o. 60, and-3 parts Tween No. 60. The resulting'emulsion'i's permitted-to cool." Surfaces coated with this emulsion are found to possess the advantageous properties describedinExample-I. I Y

"Erample IV I Ten (10) partsof polyvinyl acetate (a low molecular weight type, as soldunder the trade name Polyvinyl Acetate AYAB) are heated and melted together with 30'parts of 'Santiciz'er l-H. The hot, clear fluid is-emulsified,-witli constant agitation, in 75 parts waterheated to-19 0 E. and containing dissolved therein 4 parts Elvanol-5042, 3 parts Span No. 40, and 3 parts Tween No. 40. The emulsion is permitted to cool. Surfaces coated with this emulsionare found to possess the advantageous properties described-in Examplel g I 5 5 Twenty (20) parts on glycerol ester of hydrogenated rosin (of the type sold under the trade name Stabellite Ester No. 10) are heated and melted together with 20 parts ofK etonone E. The hot, clear fluid is emulsified, withfbonstant agitation, in 55'parts of water heatedto 190 F. and containing therein 3.0 parts lvanol 52-22, 2 parts bentonite, and6 parts"% aqueous solutionbfAerosol OT.' The emulsion is permitted to cool. (Surfaces coated with this emulsion are found to possess the advantageous properties de scribedin Example I. 1

Example VI- Thisexample particularly illustrates the use of blends of resins, to attain desired eil'ects 'with regard to adhesion to certain surfaces, temperatures at which the adhesive will become and remain tacky, and the like. I Five ,(5) parts polystyrene (molecular weight 10,000 to 15,000) are heated and melted together with 15 parts of polymerized rosin (of the type sold under the name Polypale Resin) and 50 parts, diphenyl phthalate. The resulting hot,

heated and meltedtogether with 10 parts of opal wax and parts of diphenyl phthalate. The hot, clear fluid is'emulsifi'ed in the-same manner as described in ExampleVl', and the emulsion permitted to cool. Films-formedby the emulsion driedto produce surfaces characterized by the advantageous properties already described and which were particularly notable for their slippery I u Y 1 -"Emampl VIII '[Thisexample particularly illustrates the use of flux materials, such as rosin derivatives, to increase. the compatibility of-resin and plasticizer afterheatactivation. I ,jTwent-five- (25) partsof the cooled emulsion of Example I are mixedw'ith 5 parts of Dresinol 40 (thisv being, as previously noted, the trade name of an ammonium hydroxide dispersion of modifled rosinj. This product, as compared to that of Example I, is characterized by stronger and more permanent adhesion to some surfaces, because of the more complete-compatibility achieved between resin and plasticizer.

.' 3 'Easa mple IX This example illustrates the initial merging of resin 'and'plasticizer by'solution in a common solvent, rather than by melting;

"Eightyj(80) parts o'fldiphenyl phthalate and 20 parts of polyvinyl acetate (of the grade sold under"tlie;tradename Polyvinyl Acetate V2 /2) are dissolvedin 80 (parts ethyl'acetate. The clear so1uuor 'i pourea; with continuous agitation into 11 0 "parts of waterjc mamm 4.5 parts Elvanol 5q-42fan'd 2 parts ornaraaza; When emulsificatlo islcom'plet, the. solvent is removed from the sys nigiby steam distillationor other convenient means..f;,Th e, emulsionTis'v coated upon surfaces, and whendry exhibits'the excellent characteristicspreviouslydescribedl Example X f This xample particularly illustrates the use of a binder in conjunction with the adhesive of our invention;

T0 25, 'parts'of the cooled emulsion of Example I. th'erefare' added, with agitation, 2 parts of Geon Polyblend 550x20 (this being the trade named used for a product which we believe consists of polyvinyl chloride plasticized withvHycar nitrile rubb r clear fluidis emulsified, with continuous agitation, in 75.5 parts of water maintained at 190 F. and containing dissolved therein 4.5 parts Elvanol 50-42 and 6.0 parts 25% aqueous "solution of Aerosol OT. The emulsion'is permitted to cool. Surfaces coated with this emulsion are found to possess the advantageous properties described in Example I.

Example VII Thisexample particularly illustrates the useof .waxes order to impart further increased properties of slip.and non-tackiness to'the dry adhesive film, prior to heat activation.

Ten (10) parts ofStabellite Ester: No.40 are intimate contact'with it own plasticizer.

p Asoompared'to' thef, product of Example I, this produot dries to films which show improved resistance to powdering off or crackin when the surface (i. e., label, cartonfiap, etc.) is flexed.

We are aware that itihas been proposed to mix, icy-purely mechanicalf'means, a thermoplastic resin witl'ra normally solid plasticizer-more specifically, by grinding the solid plasticizer in a ball 'millor similar comminuting equipment, and then mechanicallyfrnixing this with the resin. Contradistinguished from-this,our product, in its finalfform, prior to heat activation, consists of innumerable particles-each particle comprising a 'core' of partially plasticizedresin surrounded by and'-coated with solid plasticizer. In other words, we have here no mere mechanical mixture of resin particles and separate and discrete plasticizer particles, but, rather, a system Wherein-eaehparticle of resin is in the closest and most Furthermore, as a result iof' the emulsification step in' our process; the individual particles, both of resinandsplastici'zer, can approach considerably smaller particle size than is-jfeasibl by any mea rea our product not only produces "a more homogeneous, smoother, less grainy film, but, because of-Ethe close physical contact betweenfth'e plasticizer a'ndthe resin {the-resin'i'tself alread' being partially plasticized), it is found ftlia tied films of our adhesive are-much more readily-and completely activated-upon application. of heat, and,,,f urthermore, require lower temperatures to achieve such activation, asfcontrastedj" nexample," to more mecha ical andphysicallyseparate mixtures of plasticizers and resins. Under modern industrial methods, whereby high speed, automatic labeling and gluing machines are so widely used, this property of immediate and complete activation, at relatively lower temperatures, is of the utmost importance.

Also, not only is our product substantially improved over heretofore known materials, but our process is simpler and, therefore, economically more feasible, particularly since our method does not depend upon the relatively slow and unwieldy procedure for grinding plasticizers.

Summarizing, our process comprises, firstly, the merging or coalescing by melting or solution of a thermoplastic polymeric material and a plasticizer which is normally solid at room temperatures, and, secondly, the emulsificatio-n of the plasticized polymeric material. As additional improvements, we have described the use of waxes, fiuxes, and binders. sion of our invention, when'spread upon surfaces and dried, results in films characterized by notabl smoothness, nongraininess, and freedom from any tackiness at room temperaturesbut which become powerfully tacky and adhesive upon application of heat.

We claim:

l. The method of making a thermoplastic ad hesive composition for production of dried adhesive films which are non-tacky at room temperatures but which are activatable to a tacky and adhesive condition by heat, which consists in coalescing a thermoplastic polymeric material and an normally solid plasticizer, and in then emulsifying the resulting coalesced product yielding an emulsion of particles of th plasticized polymeric material, the plasticizer being present in a proportion greater than that which is compatible at room temperatures with the thermoplastic polymeric material to provide two plasticizer parts in the dried adhesive film of the composition, one part, being compatible with the thermoplastic polymeric material, remaining in a state of coalescence with the same and producing particles of plasticized thermoplastic polymeric material, and the other part, constituting an excess incompatible with the thermoplastic polymeric materia1, separating out from the state of coalescence therewith and forming solid plasticizer particles distributed in the thermoplastic polymeric material.

2. The method of making a thermoplastic adhesive composition for production of dried adhesive films which are non-tacky at room tem peratures but which are activatable to a tacky and adhesive condition by heat, which consists in heating and thereby fusing a thermoplastic polymeric material and a normally solid plasticizer, in then mixing with accompanying agitation the resulting heated fusion product wi h The adhesive emulheated water containing an emulsifyin agent "thereby emulsifying" said fusion i dd icr iddmg an'emulsi'on of particles of thdplasticized polymeric material, and in then coolingfltheemul-sion,

plasticizer] being present in. a, proportion greater, than that-which is? compatible at room temperatures with the thermoplastic, polymeric material-to provide ,two plasticizer part in the dried ad'hesivefilm otthecompositiQn; One part, being. compatible Withsthe; thermoplastic poly- -meric material rcm'aining in aI-state of fusion .Miththe same and producing particles of plasticized' thermoplastic polymeric material, and the other pa it, "constitutingan excess incompatible with the thermoplastic polymeric material, separating out from the state of fusion therewith and forming solid plasticizer particles distributed in the thermoplastic polymeric material.

3. The method of making a thermoplastic adhesive composition for production of dried adhesive films which are non-tacky at room temperatures but which are activatable to a tacky and adhesive condition by heat, which consists in dissolving in a common solvent a thermoplastic polymeric material and a normally solid plasticizer, and in then mixin with accompanying agitation the resulting solution product with water containing an emulsifying agent thereby emulsifying the resulting solution product yield ing an emulsion of particles of the plasticized polymeric material, the plasticizer being present in a proportion greater than that which is compatible at room temperatures with the thermoplastic polymeric material to provide two plasticizer parts in the dried adhesive film of the composition, one part, being compatible with the thermoplastic polymeric material, remaining in a state of solution with the same and producing particles of plasticized thermoplastic polymeric material, and the other part, constituting an excess incompatibl with the thermoplastic polymeric material, separating out from the state of solution therewith and forming solid plasticizer particles distributed in the thermoplastic polymeric material.

4. The method of making a thermoplastic adhesive composition for production of dried adhesive films which are non-tacky at room temperatures but which are activatable to a tacky and adhesive condition by heat, which consists in coalescing a thermoplastic polymeric material and a normally solid plasticizer, and in then emulsifying the resulting coalesced product yielding an emulsion of particles of the plasti-cized polymeric material, the plasticizer being present in a proportion by weight of one part of the polymeric material to one to five parts of the plasticizer and thereby greater than that which is compatible at room temperatures with the thermoplastic polymeric material to provide two plasticizer parts in the dried adhesive film of the composition, one part, being compatible with the thermoplastic polymeric material, remaining in a state of coalescence with the same and producing particles of plasticized thermoplastic polymeric material, and the other part, constitutin an excess incompatible with the thermoplastic polymeric material, separating out from the state of coalescence therewith and forming solid plasticizer particles distributed in the thermoplastic polymeric material.

5...The method of claim 1, in which there is incorporated in the composition a binder serving 11 as a film-forming bond between the emulsion particles of the plasticized thermoplastic polymeric material.

6. The method of claim 5, in which the binder is a resin binder the solids content 01 which is in 5 the proportion by weight of 10% based on the total weight of the emulsion.

7. The thermoplastic adhesive composition produced by the method of-claim 1. 8. A thermoplastic solid adhesive film consisting of a coating of the thermoplastic adhesive composition produced by the method of claim 1.

, RALPH C. McGAFFIN.

- ALFRED G. BATTAGLIA.

. 12 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number v Name Date 2,319,852 Doolittle May 25, 1942 2,462,029 Perry Feb. 15, 1949 2,486,756 -Murphy Nov. 1, 1949 10 2,525,671 1 Hauser Oct. 10, 1950 1 I FQREIGN PATENTS Number Country Date 501,810-v Great Britain Mar. 2, 1939 

1. THE METHOD OF MAKING A THERMOPLASTIC ADHESIVE COMPOSITION FOR PRODUCTION OF DRIED ADHESIVE FILMS WHICH ARE NON-TACKY AT ROOM TEMPERATURES BUT WHICH ARE ACTIVATABLE TO A TACKY AND ADHESIVE CONDITION BY HEAT, WHICH CONSISTS IN COALESCING A THERMOPLASTIC POLYMERIC MATERIAL AND AN NORMALLY SOLID PLASTICIZER, AND IN THEN EMULSIFYING THE RESULTING COALESCED PRODUCT YIELDING AN EMULSION OF PARTICLES OF THE PLASTICIZED POLYMERIC MATERIAL, THE PLASTICIZER BEING PRESENT IN A PROPORTION GREATER THAN THAT WHICH IS COMPATIBLE AT ROOM TEMPERATURES WITH THE THERMOPLASTIC POLYMERIC MATERIAL TO PROVIDE TWO PLASTICIZER PARTS IN THE DRIED ADHESIVE FILM OF THE COMPOSITION, ONE PART, BEING COMPATIBLE WITH THE THERMOPLASTIC POLYMERIC MATERIAL, R EMAINING IN A STATE OF COALESCENCE WITH THE SAME AND PRODUCING PARTICLES OF PLASTICIZED THERMOPLASTIC POLYMERIC MATERIAL, AND THE OTHER PART, CONSTITUTING AN EXCESS INCOMPATIBLE WITH THE THERMOPLASTIC POLYMERIC MATERIAL, SEPARATING OUT FROM THE STATE OF COALESCENCE THEREWITH AND FORMING SOLID PLASTICIZER PARTICLES DISTRIBUTED IN THE THERMOPLASTIC OLYMERIC MATERIAL. 